1. Field of the Invention
The present invention relates to a laser light intensity controller which is applied to an optical apparatus.
2. Description of the Related Background Art
An optical pickup apparatus, which is used for reading information from an optical disc or writing information into an optical disc, is provided with a laser light intensity controller which monitors a portion of a laser beam emitted from a light source to irradiate the disc with the laser beam with an appropriate light intensity.
In the laser light intensity controller, for preventing a reduction in the light intensity of a laser beam irradiated to a disc caused by the rotation of a polarization plane of the laser beam, due to a change in temperature which affects optical parts such as a light source, a portion of P-polarization component within the laser beam emitted from the light source, if the laser beam irradiated to the disc is the P-polarization component, is separated by a polarizing beam splitter, and received by a front monitor, which serves as a light receiving means, to drive the light source in response to an output signal of the front monitor (Laid-open Japanese Patent Application No. 7-326064).
However, the conventional laser light intensity controller has a problem in a large number of required optical parts and a complicated optical system.
It is therefore an object of the present invention to provide a laser light intensity controller which is capable of stably controlling the light intensity of a laser beam emitted from a light source of an optical pickup apparatus in a simple configuration, even if the plane of polarization of the laser beam rotates.
The present invention provides a laser light intensity controller for controlling a light intensity of a laser beam emitted from a light source of an optical apparatus. The laser light intensity controller includes a polarization separating device for passing therethrough most of one of an x-direction polarization component perpendicular to a direction in which a laser beam emitted from the light source travels and a y-direction polarization component parallel with the traveling direction and for reflecting a little portion of the one polarization component as monitoring light, a first light receiving device for receiving the monitoring light reflected by the polarization separating device to generate a first light intensity signal indicative of the received light intensity, and a driving device for driving the light source in accordance with the first light intensity signal, wherein the first light receiving device reflects the other of the x-direction polarization component and the y-direction polarization component and is not sensitive to the polarization component, and the first light receiving device absorbs the one polarization component and is sensitive to the polarization component.
The present invention also provides a laser light intensity controller for controlling a light intensity of a laser beam emitted from a light source of an optical apparatus. The laser light intensity controller includes a first polarization separating device for passing therethrough most of one of an x-direction polarization component perpendicular to a direction in which a laser beam emitted from the light source travels and a y-direction polarization component parallel with the traveling direction, and a little portion of the other polarization component, and for reflecting a little portion of the one polarization component and most of the other polarization component as monitoring light, a second polarization separating device for separating the one polarization component and the other polarization component from the monitoring light, a first light receiving device for receiving the one polarization component separated by the second polarization separating device to generate a first light intensity signal indicative of the received light intensity, a second light receiving device for receiving the other polarization component separated by the second polarization separating device to generate a second light intensity signal indicative of the received light intensity, a driving device for driving the light source in accordance with the first light intensity signal, and a control device for calculating effective output laser beam power of the light source in accordance with the first and second light intensity signals to control the driving device such that the effective output laser beam power is smaller than maximum rated power of the light source.
The present invention further provides a laser light intensity controller for controlling a light intensity of a laser beam emitted from a light source of an optical apparatus. The laser light intensity controller includes a polarizing beam splitter for passing therethrough most of one of an x-direction polarization component perpendicular to a direction in which a laser beam emitted from the light source travels and a y-direction polarization component parallels with the traveling direction and for reflecting a little portion of the one polarization component on a polarization separating plane as monitoring light, a reflecting member formed on a surface of the polarizing beam splitter, located on a path along which the monitoring light travels, for reflecting the monitoring light such that the reflected monitoring light exits from the polarizing beam splitter through the polarization separating plane, a light receiving device for receiving the monitoring light output from the polarizing beam splitter to generate a light intensity signal indicative of a received light intensity, and a driving device for driving the light source in accordance with the light intensity signal.